Feature: Power


Overcoming thermal challenges in high-power, high-frequency transformer designs


By Andrea Polti, Global Product Manager – Magnetics, Murata


density and reduce losses. Great strides have already been


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made in improving the efficiency of power converters thanks to advances in semiconductor technologies, where wide-bandgap devices used in resonant converter topologies allow single-stage efficiencies of over 99%. With a steady reduction in semiconductor static- and dynamic losses, attention is increasingly diverted to the heat dissipation from passive components – particularly the magnetics.


Better heat dissipation One of the desired benefits of higher converter efficiency is smaller, lighter and lower-cost heatsinking and packaging. However, to match this, magnetics in the


20 February 2023 www.electronicsworld.co.uk


s efficiency targets for power converters get more demanding, the focus is turning to the magnetic components to improve power


form of energy storage inductors, filters and transformers must also get smaller; this is typically facilitated by increasing the switching frequency. Filter and storage inductors passing DC generally require less inductance as switching frequency rises, allowing smaller cores and fewer winding turns for the same flux density. Tis produces little or no increase in total magnetic component losses if the AC component of the current is small. For transformers, core size can also


Figure 1: Murata patented transformer heatsinking


arrangement uses embedded metal plates


decrease with increasing frequency for the same number of winding turns and flux density. However, because transformer current is all AC, eddy current values and core hysteresis losses also rise substantially with rising frequency. Additionally, semiconductor dynamic losses increase with frequency, so there is always a trade-off between system frequency, efficiency, temperature rise and size. Transformers can nevertheless be very efficient, and losses are oſten disregarded


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